Sailing the North Atlantic off Norway isn't for the faint of heart. The scenery is gorgeous along the coastline's 63,000 miles of fjords, bays, and islands—what Douglas Adams called the country's "fiddly bits"—but seas are treacherous and courses labyrinthine. To sail around Stadlandet, a peninsula near Norway's westernmost point, a ship might have to go thirty-five miles out of its way. But if your voyage can wait until 2023, the captain might just take a shortcut.

The fjords of Norway are shelter from the storm.

The North Sea and the Norwegian Sea meet at the violent Stadhavet Sea, Norway's roughest waters, where storm conditions can prevail up to 106 days out of the year. Thirty-three souls have been lost to the icy waves there since the end of the World War II. Often ships will spend days waiting out the storms in the Vanylvsfjord or the Moldefjord, the narrow inlets that bracket the cliffs of Stadlandet.

Tunnels: not just for cars anymore.

Earlier this month, Norway unveiled a bold new plan to make maritime life easier around Stadlandet. A canal there is impractical, because a 1,100-foot mountain ridge runs down the center of the peninsula. So the Norwegian coastal administration huddled with an international design firm and came up with a better option: boring a mile-long tunnel right through the narrowest point of the peninsula and out the other side. It will be the world's first tunnel for ships.

A mile of rock stands between Norway and its dream.

The idea of building a shortcut through Stadlandet goes back to 1874, and the Nazis also planned a tunnel there during their occupation of Norway, but the war ended before they got around to it. Even with modern technology, this will be a whopping engineering feat: Workers boring into the mountain from both sides will excavate the tunnel downward in five layers, removing eight million tons of rock. Finally, barriers at either end of the tunnel will be blasted away, flooding the tunnel with 36 feet of seawater.

All this for the low, low price of $315 million.

When completed, the Stad Ship Tunnel will be 188 feet wide, big enough to allow passage to the 35-million-pound freight and passenger ships that ply the Norwegian coasts. Traffic lights will ensure that ships never meet head-on a thousand feet underground, and an overhead bridge could be added for pedestrians if the tunnel became a popular tourist attraction. The estimated price tag is $315 million, but boosters hope that the tunnel will pay for itself in saved accident and wait costs. But, hey, even if the numbers never work out, having a watery secret passage the width of a football field is kind of its own reward.

Explore the world's oddities every week with Ken Jennings, and check out his book Maphead for more geography trivia.